Laser-Driven Calorimetry of Single-Component Liquid Hydrocarbons

A novel laser-heating technique, referred to as the laser-driven thermal reactor (LDTR), was used to determine sample thermal (exothermic/endothermic) behavior, specific heat release rate, and total specific heat release of three volatile single-component liquid hydrocarbons, i.e., n-decane, n-butylcyclohexane and n-butylbenzene. The objective was to demonstrate measurement repeatability and extend the LDTR model from earlier investigations. The experimental apparatus consists of a copper sphere-shaped reactor mounted within a vacuum chamber, with sample and substrate supported on a thermocouple near the center of the reactor. The reactor is heated from opposing sides by a near-infrared laser to achieve nearly uniform sample temperature. The change in temperature with time (i.e., thermogram) is compared to a previously recorded baseline (no liquid sample) thermogram. A model, based on thermal energy conservation, is used to evaluate the thermograms for the thermochemical characteristics of interest. This study represents a step toward applying this technique to more complex volatile multi-component fuels of unspecified composition. Results for the LDTR were compared with a differential scanning calorimetry/thermal gravimetric analysis (DSC/TGA) instrument. The model analysis was extended to include an estimation of the hydrocarbon mass change with increasing temperature, based on the temporal change in the specific heat release rate. An estimate of the total specific heat release was obtained for these three liquid hydrocarbons and found to be consistent with the literature values when the measurements were carried out under suitable operating conditions.